Coal driving system using reheat steam

ABSTRACT

Provided is a coal drying system, and more specifically, a coal drying system using reheat steam comprising: a coal sorting device for sorting coal which has been transported by a coal transport conveyer from a coal yard, and respectively discharging the coal onto a fueling coal transport conveyer and a drying coal transport conveyer; a fluidizing reheater for storing the coal which has been sorted as fuel coal and transported into a fuel coal storage tank, and heating the fuel coal stored in the coal storage tank to a fluidized state and generating reheat steam at a specific temperature; a coal drying device for drying the coal by spraying the reheat steam generated by the fluidizing reheater on the coal, while the coal, which has been transported by the drying coal transport conveyer and passed through a coal distributing conveyer, is transported through multiple steps; and a combustion gas reheater for generating reheat steam at a specific temperature from exhaust gas generated after the coal is dried in the coal drying device by using combustion gas generated in the fluidizing reheater.

TECHNICAL FIELD

The present invention relates to a system for drying coal using reheat steam, and more particularly, to a coal drying system that removes moisture contained in the coal used as a fuel for thermal power plant by the reheat steam.

BACKGROUND ART

In general, in a thermal power plant that generates power using the coal as a fuel, coal of about 180 tons/hr per 500 MW is combusted, and the coal equivalent to about 37 tons per differentiator is supplied to a boiler. In the thermal power plant of 500 MW that uses the coal, approximately six coal yards having capacity of approximately 500 tons are installed, the normal supply of coal is performed in five of them, and the remaining one is operated as a coal storage location that preliminarily stores the coal capable of being used for a certain period of time.

Further, in the thermal power plant that generates power using the coal as a fuel, a standard thermal power design criterion of coal is designed to use a low moisture bituminous coal of 6,080 Kcal/Kg and 10% or less. Imported coal is used in some thermal power plants, and an average moisture water content of some sub-bituminous coals of them may be equal to or higher than 17%, which lowers the combustion efficiency of the boiler. When the standard thermal combustion limit is 5,400 Kcal/Kg and a heating value of the used coal is low, a decrease in the power generation amount and an increase in the fuel consumption are expected due to a decline in the combustion efficiency. Furthermore, when using the sub-bituminous coal that is a high-moisture and low-calorific coal, since the moisture content is higher than the design criteria, a conveyance system for conveying the coal is not smooth, and when grinding the coal using a differentiator, a decline in the efficiency, a decline in the combustion efficiency due to some incomplete combustion, a deviation of a heat distribution generated in the boiler, and operation in an abnormal state also occur. However, in order to reduce fuel costs in the thermal power plant, the proportion of use of the sub-bituminous coal has gradually increased to about approximately 41 to 60%.

In addition, in the face of safety issues due to expectation of global economic recovery, and destruction of the nuclear power plant caused by Japanese huge earthquake, the preference of the thermal power plant increases, and demand and price of coal seems to consistently rise. Since the environment of the global coal market changes from the consumer to the provider, stable supply and demand of coal are difficult, a production volume of the high calorific coal is expected to be maintained at current levels, and thus, an imbalance of coal supply and demand is expected.

Although the low-calorific coal is about 47% among the total deposits of the world's coal and its deposits are much, since there are problems of a low calorific value, a high moisture content and a combustion failure during combustion, and the high moisture low calorific coal has a difficulty in complete combustion, it is ignored in the market. Until recent years, worldwide, although there has been a high tendency of relying on stable prices of petroleum and low-production unit price of the nuclear power generation, many constructions of the thermal power generation that uses coal have recently been planned due to a sharp rise in the price of petroleum and a sense of insecurity to the nuclear power generation.

As conventional techniques (thermal drying) for drying the coal, a rotary drying method for drying the internal coal particles, while rotating a cylindrical shell into which coal is charged, a flash pneumatic drying method for raising and drying the high-temperature dry gas from bottom to top, while supplying the coal from top to bottom, and a fluid-bed drying method for drying the coal, while the high-temperature dry gas being raised upward along with fine particles have been mainly used.

Coal is divided into a surface moisture adhered to a gap between the coal particles, and a coupling moisture coupled to an internal pore of the coal. As the surface moisture, moisture sprayed during a cleaning process in the production area and at the time of transport and storage is most, and its amount is determined depending on a surface area and absorbency. As the particles are small, the surface area becomes greater, capillary is formed between the particles, and contains moisture, and a water content increases. The coupling moisture is formed at a generation epoch of the coal, and is low in the order of lignite, bituminous coal (bituminous coal and sub-bituminous coal), and anthracite coal. When the coal has much moisture, the heating value decreases and the transport costs also increase. Thus, it is necessary to control the moisture in the process of mixing, pulverizing, and separation of the coal.

In addition, as the relevant prior art, there are a method of converting a low-grade coal into high grade of Korean Registered Patent Publication No. 10-0960793 (published Jun. 3, 2010), and a coal drying apparatus and a system for converting coal into high grade including the same of Korean Patent Publication No. 10-2011-0098445 (published Sep. 1, 2011).

DISCLOSURE Technical Problem

An object of the present invention is to divide coal supplied from a coal yard into a fuel for generating reheated steam and a fuel for driving a generator in a thermal power plant, to dry the coal for being supplied to the thermal power plant by the use of the reheat steam after generating a reheat steam in a reheat steam generator so as to maintain the proper moisture content of the coal, thereby enhancing the heating value of coal to improve the combustion efficiency of the boiler of the thermal power plant and reduce the use of fuel.

Also, another object of the present invention is to provide a drying technique capable of preventing environmental problems due to incomplete combustion of the coal through the regulation of the moisture contained in the coal, and a technique that can be applied to a thermal power plant.

Technical Solution

According to an aspect of the present invention, there is provided a reheat steam type coal drying system that includes: a coal sorting device that sorts coal transported via a coal transport conveyer from a coal yard into a fuel coal and a drying coal and discharges the coal to a fueling coal transport conveyer and a drying coal transport conveyer; a fluidizing reheater that stores the coal sorted and transported as fuel in a fuel coal storage tank, and heats the fuel coal stored in the coal storage tank to a fluidized state to generate reheat steam at a constant temperature; a coal drying device that dries the coal by spraying the reheat steam generated by the fluidizing reheater to the coal, while the coal introduced via a coal distributing conveyer for distributing the coal is transported by the drying coal transport conveyer through multiple steps; and a combustion gas reheater that generates reheat steam at a constant temperature using exhaust gas generated after the coal is dried in the coal drying device by using combustion gas generated in the fluidizing reheater.

Further, in the present invention, the coal sorting device may include a magnetic separator that separates a metal material from coal before being charged into coal screen by a magnetic field in a coal transport conveyor, a coal screen that preliminarily separates coal of a certain particle diameter or less from the coal transported from the coal yard to the coal transport conveyor; a coal pulverizer that pulverizes the coal of a certain particle diameter or more separated from the coal screen, a two-way damper that separates the coal pulverized by the coal pulverizer into a fuel coal and a drying coal, a coal supply tank that temporarily stores the coal separated as a fuel coal by the two-way damper and then supplies the coal, and a coal pulverizer that discharges the coal through a fuel coal transport conveyor after pulverizing the coal supplied from the coal supply tank to a certain particle or less.

Further, in the present invention, the coal separated by the coal screen or separated as a drying coal by the two-way damper may be connected so as to be discharged to a drying coal transport conveyor.

Further, in the present invention, the system may include a coal distribution conveyor that distributes the drying coal into a plurality of coal dryers in the drying coal transport conveyor, a coal distribution tank that temporarily stores the coal transported by the coal distribution conveyor and then distributes the coal, and a coal fixed amount supplier that supplies the coal distributed from the coal distributor tank to the coal drying device at a certain amount.

Further, in the present invention, the system may further include a dry coal discharge conveyor that naturally cools the coal dried in the coal drying device at room temperature, a dry coal transport conveyor that transports the coal discharged from the dry coal discharge conveyor to a dry coal storage tank, and a carry-out place dust collector that collects the dust generated during transport of the coal on the dry coal transport conveyor.

Further, in the present invention, the system may further include a plurality of exhaust gas circulation blowers that sucks and blows the exhaust gas generated after the coal drying in coal drying device, and a circulation exhaust gas dust collector that collects the dust contained in the exhaust gas blown by the exhaust gas circulation blower.

Further, in the present invention, the system may further include a carry-in place dust collector that collects the dust generated during transport of the coal in the coal transport conveyor, the coal sorting device, the fuel coal transport conveyor, the drying coal transport conveyor and the coal distribution conveyor.

Further, in the present invention, the system may be configured to supply the reheat steam to each of the plurality of coal drying devices installed in the fluidizing reheater and the combustion gas reheater.

It should be understood that different embodiments of the invention, including those described under different aspects of the invention, are meant to be generally applicable to all aspects of the invention. Any embodiment may be combined with any other embodiment unless inappropriate. All examples are illustrative and non-limiting.

Advantageous Effects

According to the present invention, after sorting coal used in thermal power plant and a fuel coal for drying the coal, by generating a reheat steam using the fuel coal to remove the moisture remained inside and outside of the coal as a use fuel of the thermal power plant and prevent the incomplete combustion of coal, a calorific value of the coal is improved, the discharge of the pollutants is minimized, corrosion of the system is prevented, its durability is improved, the natural ignition rate with a decrease in moisture is reduced, the grinding efficiency of the coal differentiator and the heat distribution of the power boiler during combustion of coal are improved, it is possible to eliminate the clogging phenomenon of the path at the time of transport of coal, and it is possible to improve the stability of the coal supply by enhancing the utilization rate of the low-grade coal of the low-demand. Also, it is possible to use a low calorific coal of a price cheaper than a high-calorific coal, to reduce the fuel cost and the original cost due to a decrease in amount of coal import, and to relatively reduce the coal consumption, thereby being able to achieve an effect of reducing the emissions of waste and contaminating substances generated from the combustion gas and reducing carbon dioxide, and it is possible to expect a substitution effect of overseas techniques and an effect such as an overseas export of equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a reheat steam type coal drying system according to the present invention.

FIG. 2 is a block diagram illustrating a reheat steam type coal drying system of the present invention.

BEST MODE FOR THE INVENTION

Exemplary embodiments of the present invention will be described below in more detail with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully transport the scope of the present invention to those skilled in the art. Throughout the disclosure, like reference numerals refer to like parts throughout the various figures and embodiments of the present invention.

An embodiment relating to the reheat steam type coal drying system according to the present invention will be described in detail referring to the attached drawings.

In FIG. 1, a coal yard 10 is a place where coal for use as fuel for boilers of thermal power plants is kept and stored. The coal contains surface moisture and internal moisture. Further, water is periodically sprayed to the coal stored in the coal yard 10 to prevent scattering of coal powder. The coal stored in the coal yard 10 is transported to the coal drying system through a transport means such as a conveyor system. Further, in the coal yard 10, some of the coal transported to the coal drying system are sorted and used as reheat stem generating fuel for drying the fuel coal of the thermal power plant. Thus, the coal in the coal yard 10 is transported to the coal sorting device 100 using a coal transport conveyor CV1.

A coal sorting device 100 that sorts coal transported via a coal transport conveyer CV1 from a coal yard into a fuel coal and a drying coal and discharges the coal to a fueling coal transport conveyer CV2 and a drying coal transport conveyer CV3, respectively.

A magnetic separator 110 of the coal sorting device 100 separates a metal substance from coal before being charged into a coal screen 120 in a coal transport conveyor CV1 by a magnetic field. The magnetic separation using the magnetic separator 110 sorts the coal transported by being boarded on the coal transport conveyor CV1 into pieces of iron having magnetic properties. The coal screen 120 primarily separates the coal of a certain particle size or less from the coal transported to the coal transport conveyor CV1 from the coal yard 10. The coal of approximately 20 mm or less is separated from the coal screen 120 and is sent to the dry coal transport conveyor CV3, and the remaining coal with particle sizes greater than that is transported. At this time, the coal screen 120 is equipped with a screw conveyor or the like.

The coal crusher 130 crushes the coal of a certain particle diameter or more that is separated from the coal screen 120 and is transported. The coal crusher 130 finely pulverizes the coal by a roller formed with tooth.

The two-way damper 140 is intended to separate the coal pulverized in the coal crusher 130 into the drying coal and the fuel coal. Some of the coal separated from the two-way damper 140 is separated into a fuel coal supply tank 150 and the remaining coal is separated and transported to the drying coal transport conveyor CV3.

The fuel coal supply tank 150 temporarily stores the coal separated for fuel from the two-way damper 140 and thereafter supplies it. The coal pulverizer 160 pulverizes the coal supplied from the fuel coal supply tank 150 to a constant particle diameter or less, and thereafter, discharges the coal through the fuel coal transport conveyor CV2.

The fuel coal storage tank 210 stores the coal that is sorted and transported for the fuel from the fuel coal transport conveyor CV2. The fuel coal storage tank 210 supplies a certain amount of fuel coal to the fluidizing reheater 200 through the screw conveyor disposed at the lower end.

The fluidizing reheater 200 receives provision of the fuel coal stored in the fuel coal storage tank 210 to heat the coal to a fluidized state by the supplied flowing air and generates reheat steam of a constant temperature or more. The fluidizing reheater 200 is supplied with flame and combustion air of a burner for preheating before being ignited by being supplied with the fuel coal. Ash carbonized in the fluidizing reheater 200 is carried out to the outside through a discharge conveyor. The reheat steam generated in the fluidizing reheater 200 is supplied to one or more coal drying devices 300.

Also, the coal goes through a coal distribution conveyor CV4 that distributes the drying coal from the drying coal transport conveyor CV3 to one or more of coal drying devices 300. Further, the coal transported from the coal distributor conveyor CV4 is temporarily stored in the coal distributor tank 310, and then is distributed to the coal fixed amount supplier 320. The coal fixed amount supplier 320 supplies a certain amount of coal distributed from the coal distributor tank 310 to the coal drying device 300.

The coal drying device 300 dries the coal, by spraying the reheat steam generated in the fluidizing reheater 200 to the coal transported at a constant speed, while the coal is transported in multiple stages. Two upper and lower coal drying devices 300 are equipped, and are installed to dry the coal by spraying the reheat steam to the coal, while transporting the coal using the dryer installed in two upper and lower stages for each facility.

Further, in the coal drying device 300, the waste heat after drying the coal by the reheat steam supplied from the fluidizing reheater 200, i.e., the exhaust gas is circulated to the fluidizing reheater 200 and the combustion gas reheater 400 via the circulation exhaust gas dust collector 330 by the operation of the plurality of exhaust gas circulation blowers. The circulation exhaust gas dust collector 330 collects the circulating material contained in the exhaust gas flowed in through a plurality of exhaust gas circulation blowers and discharges it to the outside.

The combustion gas reheater 400 heats the exhaust gas generated after the coal drying in the coal drying device 300 to a reheat steam of a constant temperature, by utilizing the combustion gas flowed by being generated in the fluidizing reheater 200. That is, the combustion gas reheater 400 causes the combustion gas generated in the fluidizing reheater 200 to heat-exchange with the exhaust gas to be supplied to the coal drying system 300 again in the form of the reheat steam. The combustion gas subjected to the heat exchange in the combustion gas reheater 400 is supplied to the thermal power plant through the combustion gas induction blower, and the combustion ash separated from the combustion gas is discharged to the outside via a re-discharge conveyor.

Thus, the system is configured so that the reheat steam is supplied to each of the plurality of coal drying devices 300 installed in the fluidizing reheater 200 and the combustion gas reheater 400, and the exhaust gas discharged from the coal drying device 300 by the combustion gas discharged from the fluidizing reheater 200 is generated and circulated as a reheat steam.

In addition, the coal dried by the reheat steam in the coal drying device 300 is discharged to the dry coal discharge conveyor CV5. While the dried coal is transported to the dry coal discharge conveyor CV5, the natural cooling takes place at room temperature. Further, the coal subjected to the natural cooling in the dry coal discharge conveyor CV5 is transported to a dry coal storage tank 600 via a dry coal transport conveyor CV6. At this time, the dust collector 510 collects the dust generated during the transport of coal in the dry coal transport conveyor CV6 and discharges the dust to the outside.

Further, the coal drying system is equipped with carry-in place dust collector 500 that collects the dust generated during transport of the coal in the coal transport conveyor CV1, the coal sorting device 100, the fuel coal transport conveyor CV2, the dry coal transport conveyor CV3 and the coal distribution conveyor CV4.

In FIG. 2, the reheat steam type coal drying system transports the coal stored in the coal yard 10 and sorts the coal into fuel coal and drying coal. When the coal in the coal yard 10 is transported through the coal transport conveyor CV1, the iron metal contained in coal is separated using a magnetic field by the magnetic separator 110. The coal passing through the magnetic separator 110 is charged into the coal screen 120, and the coal screen 120 separates and discharges the coal of a constant particle size or less in the charged coal, i.e., about 20 mm or less to the drying coal transport conveyor CV3, and discharges the coal of a certain particle diameter or more to the coal crusher 130.

The coal crusher 130 sends the coal to the two-way damper 140, after pulverizing the coal to a constant particle diameter or less. The two-way damper 140 separately discharges the pulverized coal into the fuel coal and the drying coal. The two-way damper 140 discharges the drying coal to the drying coal transport conveyor CV3, and discharges the fuel coal to the coal supply tank for fuel 150. The coal pulverizer 160 discharges the fuel coal to the fuel coal transport conveyor CV2, after pulverizing the fuel coal charged from the fuel coal supply tank 150 to a certain particle diameter or less, i.e., about 5 mm or less.

The drying coal separated and discharged from the coal screen 120 and the two-way damper 140 is charged to the coal distribution conveyor CV4 via the dry coal transport conveyor CV3. The coal distribution conveyor CV4 distributes and transports the drying coal to the plurality of coal drying devices 300.

The drying coal distributed and transported in the coal distribution conveyor CV4 is charged into the coal distribution tank 310, and the coal distribution tank 310 allows the a certain amount of drying coal to be charged into the coal drying device 300 through the coal fixed amount supplier 320.

Meanwhile, the fuel coal transported via the fuel coal transport conveyor CV2 is charged into a fuel coal storage tank 210. The fuel coal of the fuel coal storage tank 210 is charged to the fluidizing reheater 200. The fluidizing reheater 200 generates a high-temperature reheat steam due to a fluidized state by the supplied flowing air after igniting the charged fuel coal. The reheat steam is a high-temperature superheated steam.

Accordingly, the coal drying device 300 dries the drying coal, by injecting the high-temperature reheat steam supplied from the fluidizing reheater 200 at the bottom of the conveyor transported in multi-stages to the drying coal charged from the coal fixed amount supplier 320. The coal drying device 300 is formed by installing the two upper and lower conveyor equipment, each of the conveyor equipment dries the coal by injecting the reheat steam to the coal, while transforming the coal using the driers installed in the upper and lower two-stages.

The dry coal dried by the reheat steam in the coal drying device 300 is naturally cooled at room temperature, while being discharged through the dry coal discharge conveyor CV5. The dry coal naturally cooled in the dry coal discharge conveyor CV5 is stored in the dry coal storage tank 600 via the dry coal transport conveyor CV6. The dry coal stored in the dry coal storage tank 600 is transported and used as fuel for boilers of the thermal power plants.

Further, the exhaust gas corresponding to the waste heat after being injected to the drying coal in the coal drying device 300 is circulated and charged to the fluidizing reheater 200 or the combustion gas reheater 400, after the circulation material is collected in the circulation exhaust gas dust collector 330 via the exhaust gas circulation blower. The combustion gas reheater 400 reheats the exhaust gas using the combustion gas discharged from the fluidizing reheater 200, generates it as the reheat steam, charges it to the coal drying device 300 and can dry the coal.

Further, in the coal drying system, the carry-in dust collector 500 collects the coal dust generated during the separation and transport of the coal in the coal transport conveyor CV1, the coal screen 120 of the coal sorting device 100 and the fuel coal supply tank 150, the fuel coal transport conveyor CV2, the drying coal transport conveyor CV3 and the coal distribution conveyor CV4. Further, the carry-out dust collector 510 collects the dust generated during the transport of coal in the dry coal transport conveyor CV6.

In this way, in the reheat steam type coal drying system according to the present invention, after separating the coal of the coal yard is separated into the drying coal fuel used in a thermal power plant and a drying coal for the reheat steam generator, the drying coal can be dried by the reheat steam, and the system improves the thermal efficiency of coal.

While particular embodiments of the present invention have been illustrated and described in the above description, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.

INDUSTRIAL APPLICABILITY

The reheat steam type coal drying system according to the present invention separates coal supplied from a coal yard into a fuel for generating the reheat steam and fuel for driving the generator in the thermal power plant, dries the coal for being supplied to the thermal power plant using the reheat stem after generating the reheat steam in the reheat steam generator, maintains the proper moisture content of the coal to enhance the heating value of the coal, thereby being able to improve the combustion efficiency of the boiler of the thermal power plant and to reduce the amount of use of fuel, and there is industrial applicability. 

1. A reheat steam type coal drying system comprising: a coal sorting device that sorts coal transported via a coal transport conveyer from a coal yard into a fuel coal and a drying coal and discharges the coal to a fueling coal transport conveyer and a drying coal transport conveyer, respectively; a fluidizing reheater that stores the coal sorted and transported as fuel in a fuel coal storage tank, and heats the fuel coal stored in the coal storage tank to a fluidized state to generate reheat steam at a constant temperature; a coal drying device that dries the coal by spraying the reheat steam generated by the fluidizing reheater to the coal, while the coal introduced via a coal distributing conveyer for distributing the coal is transported by the drying coal transport conveyer through multiple steps; and a combustion gas reheater that generates reheat steam at a constant temperature in exhaust gas generated after the coal is dried in the coal drying device by using combustion gas generated in the fluidizing reheater.
 2. The system of claim 1, wherein the coal sorting device comprises a magnetic separator that separates a metal substance from coal material using a magnetic field before being charged into a coal screen in a coal transport conveyor, a coal screen that preliminarily separates coal of a certain particle diameter or less from the coal transported from the coal yard to the coal transport conveyor, a coal pulverizer that pulverizes the coal of a certain particle diameter or more separated from the coal screen, a two-way damper that separates the coal pulverized by the coal pulverizer into a fuel coal and a drying coal, a coal supply tank for fuel that temporarily stores the coal separated as a fuel coal by the two-way damper and then supplies the coal, and a coal pulverizer that discharges the coal through a fuel coal transport conveyor after pulverizing the coal supplied from the coal supply tank to a certain particle or less.
 3. The system of claim 2, wherein the coal separated by the coal screen or separated as a drying coal by the two-way damper can be connected so as to be discharged to a drying coal transport conveyor.
 4. The system of claim 1, comprising: a coal distribution conveyor that distributes the drying coal into a plurality of coal dryers in the drying coal transport conveyor, a coal distribution tank that temporarily stores the coal transported by the coal distribution conveyor and then distributes the coal, and a coal fixed amount supplier that supplies the coal distributed from the coal distributor tank to the coal drying device at a certain amount.
 5. The system of claim 1, further comprising: a dry coal discharge conveyor that naturally cools the coal dried in the coal drying device at room temperature, a dry coal transport conveyor that transports the coal discharged from the dry coal discharge conveyor to a dry coal storage tank, and a carry-out place dust collector that collects the dust generated during transport of the coal on the dry coal transport conveyor.
 6. The system of claim 1, further comprising: a plurality of exhaust gas circulation blowers that sucks and blows the exhaust gas generated after the coal drying in coal drying device, and a circulation exhaust gas dust collector that collects the circulation material contained in the exhaust gas blown by the exhaust gas circulation blower.
 7. The system of claim 1, further comprising: a carry-in place dust collector that collects the dust during transport of the coal in the coal transport conveyor, the coal sorting device, the fuel coal transport conveyor, the drying coal transport conveyor and the coal distribution conveyor.
 8. The system of claim 1, wherein the system is configured to supply the reheat steam to each of the plurality of coal drying devices installed in the fluidizing reheater and the combustion gas reheater. 